Add initial project structure with core functionality for book and stationery uploads

- Created main application entry point in `main.go`.
- Added configuration management in `config/config.go` and tests in `config/config_test.go`.
- Implemented handlers for book and stationery uploads in `handlers/book.go` and `handlers/stationery.go`, including validation logic.
- Established database connection and services in `services/database.go` and `services/book_service.go`.
- Defined models for books and stationery in `models/book.go` and `models/stationery.go`.
- Set up Firebase integration for image uploads in `services/firebase.go`.
- Created migration scripts for database schema in `migrations/001_create_tables.sql` and subsequent updates.
- Added CORS and error handling middleware.
- Included comprehensive tests for handlers, services, and utilities.
- Documented API endpoints and usage in `README.md` and migration instructions in `migrations/README.md`.
- Introduced `.gitignore` to exclude unnecessary files and directories.
- Added Go module support with `go.mod` and `go.sum` files.
- Implemented utility functions for slug generation and validation in `utils/slug.go` and `utils/validation.go`.

handlers/health.go

@@ -0,0 +1,52 @@
+package handlers
+
+import (
+	"context"
+	"time"
+
+	"github.com/gofiber/fiber/v2"
+	"jd-book-uploader/services"
+)
+
+// HealthCheck handles health check requests
+func HealthCheck(c *fiber.Ctx) error {
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	status := fiber.Map{
+		"status": "ok",
+	}
+
+	// Check database connection
+	if services.DB != nil {
+		err := services.DB.Ping(ctx)
+		if err != nil {
+			status["database"] = "disconnected"
+			status["status"] = "degraded"
+			return c.Status(fiber.StatusServiceUnavailable).JSON(status)
+		}
+		status["database"] = "connected"
+	} else {
+		status["database"] = "not_initialized"
+		status["status"] = "degraded"
+		return c.Status(fiber.StatusServiceUnavailable).JSON(status)
+	}
+
+	// Check Firebase connection
+	if services.FirebaseClient != nil {
+		// Try to get bucket to verify connection
+		bucket, err := services.FirebaseClient.DefaultBucket()
+		if err != nil || bucket == nil {
+			status["firebase"] = "disconnected"
+			status["status"] = "degraded"
+			return c.Status(fiber.StatusServiceUnavailable).JSON(status)
+		}
+		status["firebase"] = "connected"
+	} else {
+		status["firebase"] = "not_initialized"
+		status["status"] = "degraded"
+		return c.Status(fiber.StatusServiceUnavailable).JSON(status)
+	}
+
+	return c.JSON(status)
+}